Cartilage is an avascular connective tissue made up of collagen and/or elastin fibers, and chondrocytes, all of which are embedded in a matrix. There are three main types of cartilage: elastic, fibrocartilage, and hyaline. Elastic cartilage is found in the outer ear and the epiglottis. Fibrocartilage is found between the bones of the spinal column, hips and pelvis. Hyaline cartilage can be found on the ends of bones which form joints, on the ends of the ribs, on the end of the nose, on the stiff rings around the windpipe, and supporting the larynx. Articular cartilage is a specialized type of hyaline cartilage which covers the surface of joints and provides a durable low friction surface that distributes mechanical forces and protects the joint's underlying bone.
Different types of collagen can be found in varying amounts in the collagen matrix, depending on the type of tissue. For example, hyaline cartilage, which is found predominantly in articulating joints, is composed mostly of type II collagen with small amounts of types V, VI, IX, X, and XI collagen also present. On the other hand, fibrocartilage, which can also be found in joints, is primarily composed of type I collagen. Additionally, the fibrocartilaginous tissue that sometimes replaces damaged articular cartilage is composed of type I collagen.
Loss of or damage to cartilage can lead to painful conditions such as osteoarthritis. Damage to cartilage can be caused by traumatic injury, disease and/or age. Since cartilage lacks nerves and blood vessels, it has very limited regenerative capabilities compared to other tissues. Consequently, the healing of damaged joint cartilage results in a fibrocartilaginous repair tissue that lacks the structure and biomechanical properties of normal cartilage. Over time, the repair tissue degrades and leaves damaged joint cartilage, which causes osteoarthritis and reduced movement in the joint.
A number of procedures are used to treat damaged cartilage. One common procedure includes lavage, arthroscopic debridement and repair through bone marrow stimulation. Bone marrow stimulation is generally conducted by microdrilling, abrasion or microfracture to penetrate into or through subchondral bone to induce bleeding and clot formation at the cartilage defect site. This promotes initial repair. However, the resulting formed tissue is often fibrous in nature and lacks the durability of normal cartilage. Furthermore, extensive bleeding at the defect site may also be detrimental to the joint tissues, potentially causing inflammation and degradation. Alternatively, minimal bleeding may occur such that the clot forms within the subchondral bone, resulting in insufficient migration of blood, bone marrow, cells, and the like, from the subchondral bone into the cartilage defect.
There is a need for a method for enhancing clot formation in a tissue repair site or defect site to, for example, overcome poor clot quality and prevent fibrous tissue formation over time. There is also a need for a method which limits bleeding into the joint for alleviating joint disease, pain and discomfort.